Cream butter and shortening, gradually adding sugar until light and fluffy and sugar is dissolved.,Add egg yolks, beating well.,Dissolve soda in buttermilk; add flour to creamed mixture alternately with buttermilk, beginning and ending with flour. Stir in vanilla, coconut and nuts, reserving 2 tablespoons of nuts for the top of cake.,______,Pour in 3 greased and floured 9-inch cake pans.,Bake at 350° for 30 minutes.